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Other cardioembolic causes or embolic causes from the heart area would include a valvular disease if you have a mechanical valve. And so it's interesting. There are two types of valves that are put into the heart. One is what's called a bioprosthetic valve, which is usually from pigs, a porcine valve. Those aren't much of a risk, but metal valves that the surgeon sometimes put in can be a high risk for forming blood clots in patients who have those types of middle valves are usual and very aggressive blood thinners like coumadin or Warfarin. Other areas that can cause stroke are also atherosclerosis of the aorta, if that's very severe, that can actually break off and go into the brain. Then as we move up, we go into the neck and we look for causes of stroke in the neck. And one of the biggest causes we'd be carotid stenosis. The carotid arteries are on either side of the neck and basically you have four big pipes coming in to the neck. You have two arteries that come to the back. They're called the vertebral arteries. They supply the back, the brainstem in the back of the brain. And then you've got the carotid arteries, which supply the anterior two thirds of your brain. And what can happen very frequently with diabetes, high blood pressure, high cholesterol, age, genetic predisposition, smoking, is that the carotid artery can start to become narrowed and it's usually filled with cholesterol, plaque filled with cholesterol. And if that narrows to a point, and that's usually something above 75% that can then become unstable, break off and go up into the brain causing stroke. In those types of scenarios, treatment often involves surgery and we can talk about that later.
Other cardioembolic causes or embolic causes from the heart area would include a valvular disease if you have a mechanical valve. And so it's interesting. There are two types of valves that are put into the heart. One is what's called a bioprosthetic valve, which is usually from pigs, a porcine valve. Those aren't much of a risk, but metal valves that the surgeon sometimes put in can be a high risk for forming blood clots in patients who have those types of middle valves are usual and very aggressive blood thinners like coumadin or Warfarin. Other areas that can cause stroke are also atherosclerosis of the aorta, if that's very severe, that can actually break off and go into the brain. Then as we move up, we go into the neck and we look for causes of stroke in the neck. And one of the biggest causes we'd be carotid stenosis. The carotid arteries are on either side of the neck and basically you have four big pipes coming in to the neck. You have two arteries that come to the back. They're called the vertebral arteries. They supply the back, the brainstem in the back of the brain. And then you've got the carotid arteries, which supply the anterior two thirds of your brain. And what can happen very frequently with diabetes, high blood pressure, high cholesterol, age, genetic predisposition, smoking, is that the carotid artery can start to become narrowed and it's usually filled with cholesterol, plaque filled with cholesterol. And if that narrows to a point, and that's usually something above 75% that can then become unstable, break off and go up into the brain causing stroke. In those types of scenarios, treatment often involves surgery and we can talk about that later.
There are many causes for stroke and the causes can be sort of separated out based on the type of stroke that someone has. And I think it's important because the vast majority of strokes are ischemic that we talked a little bit about the causes for ischemic strokes. And it's worth it to recognize that sort of we had the risk factors that we talked about earlier, but this is actually the direct causes. And so for ischemic strokes, what we're thinking about is and this is actually something that you'll be experiencing if you're ever in the hospital, how the physicians are approaching your evaluation because that the doctor is asking themselves, where did the stroke come from? And specifically there's a clot that landed in an artery in the brain, where did that come from? And so the possibilities that we sort of consider are going to be one. And basically you can just start from here and you work your way up. Did it come from the heart? And we think about irregular heart rhythms that can occur and far and away the most common irregular heart rhythm in people over the age of 50 and the cause of probably close to 20% of all strokes is an irregular heart rhythm called A fib: Atrial fibrillation.
Among some less common but important causes of stroke is something called a dissection. This is a type of or cause of stroke that is much more common in young people. Amongst the most common causes of stroke in young people, in fact. And a dissection is where the artery, and it could be any of the major arteries going up into the brain, gets injured or torn from trauma. And what happens is you can think of the arteries having multiple layers and there's the outside layer and the inner layer. And what'll happen is the inner layer from the trauma gets torn up and that exposes this basement that should never be exposed to blood and blood clots can form on that. And then the blood clots can go up into the brain and cause strokes. That's an important thing to recognize. And again, this is something we see in young people often proceeded by trauma. And I can give you a good example of a patient I saw not too long ago who was a hockey player and was involved in an active hockey game the night before. Came home and often when you have a dissection, there's some pain. and the next day had a stroke related to a torn artery. And we can talk about the treatment of that a little bit later, but it does involve more aggressive blood thinners for approximately three months.
Another cause is worth at least recognizing is an infection of the heart. Something called bacterial endocarditis. This can happen in all kinds of circumstances where someone has a blood infection. It can come from IV drug use, but it can happen also in other circumstances where there is no IV drug use. And when the heart gets infected, it often is sort of nebulous. The symptoms can be fatigue, night sweats, weight loss, fevers, and no one can figure out why. And it has to be evaluated with a specific type of echocardiogram called the transesophageal echocardiogram where they actually stick the tube in the throat to look at the heart from the esophagus where there's no hard sternum in the way. And we can see the bacterial that the bacteria growth on the valve of the heart, which can break off and go up into the brain. And that's a specific type of stroke that's treated oddly enough, not with blood thinners, but with antibiotics.
Lastly, in the back of the brain where you've got two separate arteries coming up with a back called the vertebral arteries, they supply the brainstem and an area of the brain called the Cerebellum, which is involved in coordination. And so with strokes that occur there, these can be much more difficult and actually much more dangerous. With respect to symptoms in that area, the cerebellum is involved in coordination. So if you want to pick up something, if I had a cup here and I wanted to pick it up, it takes all of these different muscles. My, my deltoid, my biceps, my triceps, all these muscles, it takes a plan so that they're coordinating their movement and a nice smooth movement. And your cerebellum is what does that, when the cerebellum doesn't work, that same nice, smooth movement would look something along the lines of this with each muscle overcompensating and over doing what it's supposed to do. And so people can have balance issues and ability to stand. Walk. When the brainstems involved, other things can happen. Like you can develop vertigo, which is a sense of the room is spinning, double vision, sudden slurred speech. And these are all signs of brainstem strokes that can be quite dangerous. And again, I point out very difficult for the clinician or for the provider to sort of nail down because they're hard to detect.
So when it comes to a stroke, it's important to recognize what the signs and symptoms of stroke are. But to understand that very well, it's important to sort of recognize maybe some of the anatomy of the brain and anatomy, the blood vessels. And so the first thing to sort of realize is that your brain is sort of cut right down the middle and there's blood flow on the right side of the brain and there's blood flow in the left side of the brain. And because of that, the symptoms are very frequently lateralized. And so that's actually an important part of how when I see somebody, if I'm thinking about stroke, how I evaluate them, I'm looking for these lateralized signs. And so the idea here is that if a blood clot were to travel up the carotid artery and, and land somewhere in the brain, say on the right side, while I could envision that the right side of the brain controls the left side of the body, so they can have numbness or weakness on the left side, they could have vision changes on the left side. And now on the flip side, if it were to come up the left side, it would affect the right side of the body.
Another important thing to sort of recognize is that language and your brain is lateralized. In the vast majority of people language is on the left side of the brain. Sometimes it can be on the right side of the brain, but the vast majority is on the left. And so when a stroke involves the language area, it can be sometimes hard to recognize because it just seems like that person's confused or acting strangely, they may not even have any weakness at all. But when languages is involved, we call that aphasia and people can have a few different issues. They can have a difficult time expressing words so people can, people can often say, I know what I want to say, but I can't get the words out. That occurs when a stroke involves the inferior frontal lobe on the left side in the area of the brain called the Broca's area or another area of language is in the back of the brain and the temporal lobe called Wernicke's area. And when a stroke occurs there, people aren't able to comprehend things so they can talk but it doesn't make any sense. They will often sort of say word salad. They'll say things that don't make sense or it can be actually kind of tough. You know, you can walk into a room with somebody and you know, they'll sort of read your body cues and say very simple nonspecific things that sound like it sort of makes sense. Like, hey, how you doing? But if you ask them very specific things like, can you show me two fingers? They can't comprehend that and do it. So those can be dangerous and easy to miss.
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